Engines may use various forms of fuel delivery to provide a desired amount of fuel for combustion in each cylinder. One type of fuel delivery uses a port injector for each cylinder to deliver fuel to respective cylinders. Still another type of fuel delivery uses a direct injector for each cylinder.
Engines have also been described using more than one injector to provide fuel to a single cylinder in an attempt to improve engine performance. Specifically, in US 2005/0155578 an engine is described using a port fuel injector and a direct injector in each cylinder of the engine.
Another approach utilizing multiple injection locations for different fuel types is described in the papers titled “Calculations of Knock Suppression in Highly Turbocharged Gasoline/Ethanol Engines Using Direct Ethanol Injection” and “Direct Injection Ethanol Boosted Gasoline Engine Biofuel Leveraging for Cost Effective Reduction of Oil Dependence and CO2 Emissions” by Heywood et al. Specifically, the Heywood et al. papers describe directly injecting ethanol to improve charge cooling effects, while relying on port injected gasoline for providing the majority of combusted fuel over a drive cycle.
The inventors have recognized various issues associated with such systems. Injection and other control strategies in these systems are predicated on availability of a knock-suppressing agent such as ethanol, and effective delivery of that agent into the combustion chamber. However, deficiencies in the ethanol delivery, such as a malfunction in the ethanol injector or a depleted or low ethanol supply, can result in engine knock, elevated exhaust temperatures, accelerated component wear, and/or other potentially undesirable effects.
Thus, in one approach, a system is provided for an engine, the system having a cylinder and first and second fuel injection subsystems. The first fuel injection subsystem is configured to inject a first fuel into the cylinder, and the second fuel injection subsystem is configured to inject a second fuel into the cylinder. The system also includes an electronic engine controller configured to control a plurality of operating parameters of the engine. The electronic engine controller is configured to cause variation of at least one of the operating parameters in response to a shortfall condition of the second fuel injection system. The shortfall condition may include detection of a condition indicative of a current or potential future deficiency in the second fuel injection subsystem, which may be configured to provide a knock-suppressing agent such as ethanol into the cylinder. Thus, the detected deficiency in the knock-suppressing agent is accounted for in the control strategies of the engine, so as to maintain knock-suppression and other desired performance characteristics.